1. Field of the Invention
This invention relates to stabilized polyurethane, polyurea and polyurethane-polyurea polymers. More particularly, the present invention relates to using hydrazide functionalized hindered amine light stabilizers (HALS) for stabilizing polyurethane, polyurea and polyurethane-polyurea polymers against the degradative effects of heat and/or light. The HALS of this invention have both an amide group and a hydrazide group for enhancing the photostabilization efficiency of the HALS. Furthermore, the hydrazide functionality is used to bond the HALS into the polyurethane, polyurea and polyurethane-polyurea polymer.
2. Description of the Prior Art
Polyurethanes, polyureas and polyurethane-polyurea polymers are extremely versatile and important classes of polymers, widely used in fabricating molded parts, foamed parts and fibers. When exposed to actinic radiation, polyurethane, polyurea and polyurethane-polyurea polymers degrade at varying rates depending on temperature, structure and light intensity.
Typically, stabilizers are added to polyurethane, polyurea and polyurethane-polyurea materials to preserve the useful lifetime of the materials. HALS have been shown to be effective light stabilizers for polyurethanes, polyureas and polyurethane-polyureas, particularly when used with other stabilizers, such as UV absorbers. See G. Capocci, "Advances in the Light Stabilization of Polyurethanes," Plastics Compounding, May/June 1987, pp. 13-14, 16, 18, 25-27.
Using hydrazide-substituted HALS for permanently stabilizing a polyurethane, a polyurea and a polyurethane-polyurea is generally known in the art. For example, U.S. Pat. No. 4,178,279 discloses a permanently stabilized polyurethane comprising HALS moieties chemically attached to the polyurethane molecule by a urethane linking group or a urea linking group. A process is disclosed for preparing the stabilized polyurethanes by incorporating the reactive HALS into the polymer formulation.
In its more preferred embodiments, U.S. Pat. No. 4,178,279 discloses using previously known HALS hydrazides having the general formula: ##STR1## R, R.sup.1 and R.sup.2 are as defined in the patent and are not relevant for the purpose of the present invention. R.sup.4 is hydrogen, --C(.dbd.O)--NH--NH.sub.2 or, when R.sup.3 is hydrogen, a straight chain or branched chain alkyl group of 1 to 20 carbons, a cycloalkyl group of 5 to 12 carbons, an aralkyl group of 7 to 12 carbons, an omega-cyanoalkyl group or a beta-alkoxy carbonylalkyl group. When R.sup.3 is a straight chain or branched chain alkyl group of 1 to 20 carbons, a cycloalkyl group of 5 to 12 carbons, an aralkyl group of 7 to 12 carbons, an omega-cyanoalkyl group or an alkoxy carbonylalkyl group, R.sup.4 is an omega-hydroxyalkyl group, an omega-N-alkylaminoalkyl group, an omega-hydroxyalkyl group or an omega-carboxylic acid hydrazidoalkyl group. In addition, when R.sup.3 and R.sup.4 do not contain an active hydrogen-containing group, for example, --NH.sub.2 or --OH, R may also be an omega-aminoalkyl group, a beta-hydroxyalkyl group or a beta-carboxylic acid hydrazidoalkyl group.
U.S. Pat. No. 4,145,512 discloses permanently stabilized polyurethanes having polymer segments represented by the following formula: ##STR2## Y is derived from a diisocyanate or diisocyanate prepolymer and R is any one of several known HALS substituents. R.sup.1 and R.sup.2 are straight chain or branched chain alkyl groups or R.sup.1 and R.sup.2 are linked together to form a cycloalkyl ring. A is a direct bond, an omega-hydroxyalkyl group, an omega-aminoalkyl group, an omega-carboxylic acid hydrazido group, an omega-semicarbazido group or an omega-carbazic ester group. B is an omega-hydroxyalkyl group, an omega-aminoalkyl group, an omega-carboxylic acid hydrazido group or an omega-semicarbazido group. The presence of the above polymer segments in the polyurethane is selected to provide 0.05% to 5% by weight of HALS groups in the polyurethane.
Although not considered "prior art," copending U.S. Pat. application Ser. No. 310,408, filed Feb. 13, 1989, now U.S. Pat. No. 4,983,738, and abandoned parent U.S. Pat. application Ser. No. 84,602, filed Aug. 12, 1987, both assigned to the assignee of the present invention and application, disclose N-(2,2,6,6-tetraalkyl-4-piperidinyl)amic acid hydrazides having the general formula: ##STR3## These amic acid hydrazides correspond to Formula III of the present invention, the hydrazide group providing a means of attaching the light stabilizer to isocyanate-containing polymers or monomers.
Although also not considered prior art, copending U.S. Pat. application Ser. No. 454,889, filed Dec. 22, 1989, now U.S. Pat. No. 5,043,372, assigned to the assignee of the present invention and application, discloses N,N'-hydrocarbylenebis-[N-(2,2,6,6-tetraalkyl-4-piperidinyl]amic acid hydrazides having the general formula: ##STR4## These amic acid hydrazides are efficient light stabilizers, the hydrazide groups providing means of attaching the light stabilizer to a suitable coreactive polymer.
The presence of a second amide group in the HALS-hydrazide moiety of the present invention is a major distinction from the prior art and advances the technology of stabilizing polyurethanes and polyureas and mixtures thereof with HALS. As indicated, this additional amide group enhances the photostabilizing effectiveness of the HALS stabilizer.